changelog for plotlyjs bump

Author: alexcjohnson

CHANGELOG.md

@@ -5,6 +5,20 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ## [Unreleased]
 
 ### Changed
+- [#1869](https://github.com/plotly/dash/pull/1869) Upgrade Plotly.js to v2.4.2. This includes:
+  - [Feature release 2.5.0](https://github.com/plotly/plotly.js/releases/tag/v2.5.0):
+    - 3D traces are now compatible with `no-unsafe-eval` CSP rules.
+  - [Feature release 2.6.0](https://github.com/plotly/plotly.js/releases/tag/v2.5.0):
+    - Add `smith` subplots and `scattersmith` traces, for drawing Smith charts.
+  - [Feature release 2.7.0](https://github.com/plotly/plotly.js/releases/tag/v2.5.0):
+    - Add text data for `histogram` traces.
+    - Fix an interaction between `uirevision` and `autorange` that pops up in some cases of mixed clientside / serverside figure generation.
+  - [Feature release 2.8.0](https://github.com/plotly/plotly.js/releases/tag/v2.5.0):
+    - Add horizontal colorbars.
+    - Add text data on `heatmap` and related trace types.
+    - Control legend group title fonts.
+  - Patch releases [2.5.1](https://github.com/plotly/plotly.js/releases/tag/v2.5.1), [2.6.1](https://github.com/plotly/plotly.js/releases/tag/v2.6.1), [2.6.2](https://github.com/plotly/plotly.js/releases/tag/v2.6.2), [2.6.3](https://github.com/plotly/plotly.js/releases/tag/v2.6.3), [2.6.4](https://github.com/plotly/plotly.js/releases/tag/v2.6.4), and [2.8.1](https://github.com/plotly/plotly.js/releases/tag/v2.8.1) containing bugfixes.
+  - This PR also upgrades various other dependencies of dash renderer and component suites.
 
 - [#1745](https://github.com/plotly/dash/pull/1745):
     Improve our `extras_require`: there are now five options here, each with a well-defined role: